The present invention relates to a process for covering a cut edge of an opening of a container with a protective covering layer, including a tube-shaped area covering the cut edge, a plane area adhering to the outer surface of the container and a plane area adhering to the inner surface of the container.
The present invention relates further to a container comprising at least one container wall which has an opening with a cut edge being covered by a protective covering layer which covers at least a part of the inner surface and the outer surface of the container wall.
U.S. Pat. No. 4,397,401 describes a process for covering a cut edge in which a protective covering layer is made from two sheet-like foil pieces. The two foil pieces of foil are applied to the container wall which comprises the opening. One foil piece is laid onto the outer surface, and the other foil piece is laid onto the inner surface of the container wall, whereby the opening of the container wall is completely covered by the associated foil piece. The cut edge is covered in that one foil piece, or both foil pieces are formed from the surface of the container wall in through the opening. Both foil pieces are melted together in the area of the cut edge so that a single protective covering layer is made which, as a result of the melting, adheres to the cut edge. An opening is made in both pieces of foil, and the opening of each has a smaller cross section than that of the original opening of the container wall, which comprises a cut edge to be covered. The material separated from the two foil pieces during the setting in of the openings is fed off as waste.
In the known process, the tube-shaped area which covers the cut edge arises from processes of shaping, melting and the setting in of openings in both the foil pieces. The two plane areas of the protective covering layer bordering the tube-shaped area are formed by the portions of both pieces of foil which are applied to the surfaces of the container wall but not formed.
U.S. Pat. No. 4,116,359 describes the filling openings of tin cans being closed by a so-called pull tab which is made of an aluminum layer and a synthetic foil adhered to same. While the pull tab is partly pressed into the filling opening by a punch, the synthetic foil is pulled off to lay around the edge of the filling opening.
It is an object of the present invention to provide an edge protection in a container which is simple and cost-effective to produce.
This object has been achieved in a process according to the present invention by producing the protective covering layer from a single foil piece which is applied to the container wall comprising the opening and then formed, wherein at least one of the plane areas is formed and adhered to the container wall.
The object has also been achieved in a container according to the present invention by making the protective covering layer from one piece of material to cover only the area of the outer surface of the container wall which borders the opening.
The process and form of the protective covering layer according to the present invention lead to a significant simplification in relation to the production and the application of the protective covering layer in the cut edge. The foil materials are not melted in the area of the cut edge, nor are melted foil pieces adhered to same.
Single pieces of foil of various forms can be used for the protective covering layer which afford a low labor-consuming application to the opening. Depending on the shape of the foil supplied, a smaller or larger number of procedural steps for applying it to the cut edge must be carried out. The foil can be supplied already pre-formed to such a degree that only one of the plane areas must be produced by forming the foil and adhered to the container wall.
The plane areas of the protective covering layer are adhered to the inner and outer surfaces of the container wall after feeding and forming of the foil. The tube-shaped area of the protective covering layer which covers the cut edge does not need to be adhered thereto. It is, however, possible in certain embodiments of the invention to adhere the protective covering layer to the cut edge.
Whatever the form of the fed foil, either no foil material waste or very little waste is produced by the manufacture and application of the protective covering layer to the cut edge. In contrast to known processes, a significant saving in material is thus achieved.
The present invention can be applied usefully to all containers where it is to be avoided that a medium, in particular the liquid contents, leaks into the container wall. In the area of the opening, the surface of the container wall is often broken open, such as then when the opening is produced by cutting or punching. By applying the protective covering layer, the same or a similar protection can be made in the area of the edge as exists in the other areas of the container irrespective of the outer shape of the container. The foil is advantageously formed and/or adhered to the container wall with the aid of heat. Heat sealing is particularly suitable method in this regard.
An advantageous aspect of the present invention is the use of a foil for the production of the protective covering layer which is formed from a plane section and a tube-shaped section. It is thereby possible to feed the foil in this form to the container wall or to produce this form at the container wall after the foil has been fed thereto. The plane section is laid and adhered onto the inner surface or the outer surface of the container wall, whereby adhering can take place before or after the complete forming or simultaneously with the complete forming of the foil into the protective covering layer. The plane section of the foil laid and adhered onto the surface forms one of the two plane areas of the protective covering layer.
The tube-shaped section is guided into the opening of the container wall to cover the cut edge of the opening while a portion projects out of the opening. The part of the tube-shaped section of the foil lying inside the opening forms the tube-shaped area of the protective covering layer which covers the cut edge. As already mentioned, the tube-shaped section can be formed before or after the foil is fed by forming the foil at the container wall.
The portion of the tube-shaped section of the foil which projects out of the opening of the container wall is formed and adhered to the container wall surface which is opposite the plane section of the foil. The second plane area of the protective covering layer is thus formed.
In one advantageous embodiment of the present invention, the foil has a sheet-like form, from which the tube-shaped section is formed. It is advantageous when an opening is made in the sheet-like foil, whereby the border area is formed into the tube-shaped section.
The foil is advantageously laid against the inner surface of the container wall and adhered thereto such that the plane section of the foil forms a protective layer for at least one part of the container inner surface. In this embodiment, the protective layer normally provided for the container inner surface can also be used as a protective covering layer for the cut edge of the container opening.
In another advantageous embodiment, the foil is laid against the inner and outer surfaces of the container wall so that only the area of the inner surface and/or of the outer surface bordering on the cut edge of the container wall is covered.
In a still further advantageous embodiment, the foil fed to the container wall has a tube-shaped form guided into the opening so that a portion covering the cut edge, a portion rising over the outer surface above the opening and a portion rising over the inner surface above the opening are formed. After the pre-formed foil has been fed to the container wall, each of the portions rising above the opening are formed again and adhered against those container wall surfaces which are turned theretowards. The portions now formed again and adhered against the surfaces of the container wall form the plane areas of the protective covering layer. The tube-shaped area of the protective covering layer is formed from the rest of the tube-shaped foil which remains inside the opening.
In a container with an edge protection according to the present invention, a protective covering layer is applied at the cut edge of the container opening. The protective covering layer is made from one piece of material and only covers the area of the outer surface of the container wall bordering the opening.
In an advantageous development of the present invention, the protective covering layer covers only the area of the inner surface of the container wall bordering the opening. The protective covering layer then has a rivet-like form and can be manufactured with a very small amount of material.
Another advantageous aspect of the present invention is that the protective covering layer is formed to cover the inner surface of a container lid. It is advantageous when the protective covering layer which covers the lid simultaneously forms the protective layer of the inner lid surface. The protective layer usually necessary for a container to prevent the contents from leaking through to the container wall inner surface is then used at the same time as a protective covering layer for the cut edge of the container opening. The procedure can then be removal of the cardboard in the area of the opening, punching a hole in the protective layer and then placing the protective layer around the edge to be protected.
Advantageously, a pull tab is adhered to the container wall outer surface. The pull tab can be attached to the protective covering layer of the cut edge, for example after the container has been filled, so that the opening is closed in a leak-proof way.
The production of a container with a protective coating along an edge segment is described in our copending application Ser. No. 08/418,798, filed Apr. 7, 1995, now allowed. The disclosure therein is incorporated herein by reference.